Free calcium ion concentration is known to govern numerous biological processes and indeed calcium acts as an important biological secondary messenger for muscle contraction, neurotransmitter release, ion-channel gating, and exocytosis. As such, the development of molecules with the ability to instantaneously increase or diminish free calcium concentrations potentially allows greater control over certain biological functions. In order to permit remote regulation of Ca2+, a selective BAPTA-type synthetic receptor / host was integrated with a photoswitchable azobenzene motif, which upon photoirradiation would enhance (or diminish) the capacity to bind calcium upon acting on the conformation of the adjacent binding site, rendering it a stronger or weaker binder. Photoswitching was studied in pseudo-physiological conditions (pH 7.2, [KCl] = 100 mM) and dissociation constants for azobenzene cis- and trans-isomers have been determined (0.230 μM and 0.102 μM, respectively). Reversible photoliberation/uptake leading to a variation of free calcium concentration in solution was detected using a fluorescent Ca2+ chemosensor.
游离钙离子浓度已知能够控制许多生物过程,事实上,钙作为肌肉收缩、神经递质释放、离子通道控制和分泌作用的重要生物次级信使。因此,开发具有瞬间增加或减少游离钙离子浓度能力的分子,潜在地允许更好地控制某些生物功能。为了允许远程调节Ca2+,选择性的BAPTA型合成受体/宿主被与可光切换的偶氮苯基团集成,光照后会增强(或减少)结合钙离子的能力,通过作用于相邻结合位点的构象,使其成为更强或更弱的结合物。在伪生理条件下(pH 7.2,[KCl] = 100 mM)研究了光切换,确定了偶氮苯和异构体的解离常数(分别为0.230 μM和0.102 μM)。使用荧光Ca2+化学传感器检测到可逆的光解放/吸收,导致溶液中游离钙离子浓度的变化。